1. Field of the Invention
The present invention relates to an indicator and a display apparatus, and especially to the display apparatus having a display device such as an LCD positioned at the center of a scale for a rotary pointer.
2. Description of the Related Art
A conventional display apparatus has a display device viewed from a front side through a scale for a rotary pointer. This arrangement provides an open view of the display device without obstruction of the pointer.
The scale usually shows important information such as a speed of a vehicle, and the display device shows unimportant information such as a current time. It is thus desirable to arrange the scale in front of the display device to increase visibility of the scale.
One indicator has a pointer with an inversed S-shape at an end portion thereof to remove interference between the display device and the pointer and to be appeared over the scale.
This indicator has a LED light source surrounding an axle of the rotary pointer to achieve a uniform illumination. However, it is difficult to obtain the uniform illumination at a distal end of the pointer due to the complicated shape requiring for many reflection surfaces. The many reflection surfaces reduce luminance due to attenuation of light.
FIGS. 6-7 show a display apparatus solving the above problem (JP 2010-19619 A). The display apparatus 100 includes an LCD device 101 as a display device, a scale 102, a main board, a motor 104, and a pointer 105. The LCD device 101 displays several information such as a warning signal and a current time.
An index (e.g., number) is printed on a front surface of the scale 102 so that the pointer 105 points the index. The main board 103 is disposed rearwardly of the LCD device 101. A main body 104A of the motor 104 is mounted on a rear face of the main board 103 and a rotation axle 104B of the motor 104 is projecting forwardly from the main board 103. The pointer 105 includes a board 105A, an LED light source 105B, a light guide portion 105C, an attachment portion 105D (FIG. 7), and a balance weight portion 105E. The board 105A is attached to the rotation axle 104B and extends radially outwardly from the rotation axle 104B.
The LED light source 105B is disposed at the distal end and a front face of the board 105A to emit light forwardly. The light guide portion 105C includes optical guiding members of a first member 105C-1, a second member 105C-2, a third member 105C-3, and a pointer portion 105C-4. The first member 105C-1 is upstanding forwardly along the axial direction of the rotation axle 104B, and a lower end thereof faces the LED light source 105B. The second member 105C-2 extends radially inwardly from an upper end of the first member 105C-1 toward the rotation axle 104B. The third member 105C-3 is upstanding forwardly from an inward end of the second member 105C-2 along the axial direction of the rotation axle 104B. The pointer portion 105C-4 extends radially outwardly from an upper end of the third member 105C-3.
The attachment portion 105D has a top wall 105D-1 allowing force-insertion of the lower end of the first member 105C-1, and a pair of side walls 105D-2 extending downwardly from opposite side edges of the top wall 105D-1. The pair of the side walls 105D-2 have opposed slide grooves allowing insertion of opposite edges of the board 105A to fasten the light guide portion 105C to the board 105A. The balance weight portion 105B is oppositely disposed with respect to the LED light source 105B and attached on a rear surface of the board 105A in order to balance the weight of the board 105A, the LED light source 105B and the light guide portion 105C about the rotation axle 104B.
The display apparatus 100 has the pointer 105 with the LED light source 105B disposed on the board 105A fixed on the rotation axle 104B so that the LED light source 105B rotates together with the pointer 105. This arrangement removes non-uniformity of illumination of the rotating pointer 105. Referring to FIG. 6, the pointer 105 includes three reflection surfaces M11, M12 and M13 to guide a light L from the LED light source 105B to a front end of the light guide portion 105C. This arrangement has less reflection surfaces and improves the luminance of the light guide portion 105C.
The pointer 105 has a center of gravity in the attachment portion 105D with respect to the rotation axle 104B and it is thus difficult to provide the balance to the pointer 105. The imbalance of the pointer 105 causes backlash between the light guide portion 105C and the attachment portion 105D, and between the attachment portion 105D and the board 105A, resulting in reduction of accuracy of the pointer 105. The backlash may cause a displacement between the LED light source 105B and the light guide portion 105C, resulting in reduction of luminance of the light guide portion 105C.
The large sized attachment portion 105D may reduce the backlash between the attachment portion 105D and the board 105A. However, the large sized attachment portion 105D increases the weight of the pointer 105 and prevents lightweight. The LED light source 105B is positioned away from the rotation axle 104B, resulting in increase of the weight of the balance weight portion 105E and preventing the lightweight of the pointer 105.
This arrangement also causes increase of size of the board 105A, resulting the increase of entire weight of the pointer 105. The pointer 105 can be lightweight by decreasing size and thickness of the board 105A. However, the decrease of the size reduces rigidity of the pointer 105 and the decrease of the thickness causes thermal deformation of the pointer 105 as well as the decrease of the rigidity. JP 2009-128257 A and JP 2008-20387 A disclose other pointers having different shapes.